The present invention refers to an apparatus for protecting the walls of particular cylinders during the thermal coating of the walls of other cylinders of an engine block.
Nowadays, in manufacturing combustion engines, more and more engine blocks made of a light metal alloy are used whose cylinder walls are provided with an iron-containing coating layer applied by means of a thermal spraying apparatus. Thereby, for applying that coating, preferably plasmatrons are in use that have a rotating spraying head. Since, normally, not all cylinder walls of an engine block can be coated simultaneously, those cylinder walls that are not subjected to the thermal spraying operation have to be protected from contamination.
Particularly in the case of engine blocks of so-called V-engines or flat engines, this is of increased importance since one row of cylinders is located opposite another row of cylinders, with the result that the cylinder walls of the row of cylinders opposite to the one that is actively coated can be contaminated. Such a contamination can be caused, for example, by particles sprayed towards the cylinder wall to be coated, but do not adhere thereto. Moreover, by the flow of gases inevitable during a thermal coating operation, also dust particles are entrained which can deposit on the walls of the cylinders not subjected to the coating operation, thus leading to an undesired encapsulation of particles in the coating subsequently to be applied to that particular cylinder wall.
It is an object of the present invention to provide an apparatus for protecting cylinder walls of an engine block during a thermal coating operation that is of simple design and can be easily and quickly used.
To meet these and other objects, the present invention provides an apparatus for protecting the walls of particular cylinders during the thermal coating of the walls of other cylinders of an engine block. The apparatus of the invention comprises a plurality of hollow body members having a first outer diameter that is smaller than the diameter of a cylinder bore to be protected. The hollow body members are inflatable to a diameter that is greater than the diameter of the cylinder bore to be protected. The apparatus further comprises means for moving the hollow body members into the cylinders whose walls are to be protected and for removing the hollow body members therefrom when they have the afore mentioned first diameter. Finally, means are provided for inflating the hollow body members when they are moved into the cylinders whose walls have to be protected, and means for deflating the hollow body members prior to actuating the means for removing the hollow body members from the cylinders whose walls are to be protected.
By providing an apparatus for protecting the cylinder walls of engine blocks during the coating of particular cylinders, which comprises inflatable hollow body members that can be moved into the cylinders and inflated therein, the walls of those cylinders located opposite the cylinders subjected to the coating operation can be easily and efficiently protected from contamination.